The invention relates to a method for calibrating an optical arrangement comprising a camera and a projector. The invention further relates to a coordinate measuring machine having such an optical arrangement and implementing the calibration method.
A method of the afore-mentioned type is disclosed by DE 195 36 297 A1. A projector is used to project a predetermined pattern onto a projection area which, for example, is on a calibration plate. The projection area or the calibration plate is introduced into the measurement volume in advance. Then, a coordinate with respect to a first axis in the coordinate system of the measurement volume is determined for a pattern point in the projected pattern, said first axis preferably being perpendicular to the projection area (e.g. z-axis). The optical arrangement may be calibrated with respect to the first (z-)axis on the basis of the determined first coordinate.
Further methods known from the prior art use plane plates with markers which have been applied in a highly precise manner. However, such plane plates are expensive. Moreover, a whole-area distortion measurement is not possible with such an arrangement, and so the accuracy of the calibration is limited.
Another disadvantage afflicting the aforementioned known methods is that these require a plurality of calibration steps with different components, the spatial assignment of which is only possible with much effort.